17  Unit 4: Earth-Sun Dynamics 5E

What factors have contributed to climate change in the past and are they contributing to climate change now?

Author

Earth & Space Science

HS-ESS2-4 Time: 5 Days

🌍 MYSTERY: Earth’s Climate Cycles 🌍

17.1 🔬 THE PHENOMENON

⚡ The amount of solar radiation hitting 65°N has been CYCLING UP AND DOWN for 750,000 years — repeating the same pattern every ~100,000 years! ⚡

17.1.1 🤔 THE BIG QUESTIONS:

  • 🌀 Could natural cycles be causing today’s climate change?
  • 🛸 How has Earth’s position in space changed over time?
  • 🔥 What happens to Earth’s temperature when our orbit shifts?

18 Engage: Solar Radiation Patterns

18.1 Solar Radiation at 65°N

Connecting to our earlier questions about how Earth’s temperature has varied in the past, let’s analyze the total amount of energy from solar radiation reaching Earth at 65°N over the last 750,000 years.

18.1.1 🎯 DETECTIVE MODE: What Do You See?

  1. 🔍 What repeating pattern jumps out at you in the last 750,000 years?
  2. ⏰ How often does the radiation peak?
  3. 🧊 Could this pattern explain Ice Ages?

🤯 WAIT — this pattern has been repeating for THREE-QUARTERS OF A MILLION YEARS?! Let’s find out WHY… 🤯

19 Explore: Earth’s Orbital Cycles

19.1 🎢 The THREE ORBITAL CYCLES

MISSION: Use these interactive models to gather evidence about Earth’s position in space. Could these orbital wobbles and stretches be causing the 100,000-year radiation pattern we just saw?

💡 DID YOU KNOW? In 1941, Serbian scientist Milutin Milankovitch figured out that Earth’s “wobbles” in space control Ice Ages. Mind = blown! 🤯

19.1.1 🔵 Cycle 1: ECCENTRICITY (~100,000 years)

THE STRETCH: Earth’s orbit changes from nearly circular ⭕ to more elliptical 🥚

19.1.2 🌐 Cycle 2: OBLIQUITY (Axial Tilt) (~41,000 years)

THE WOBBLE: Earth doesn’t spin perfectly upright! Our axial tilt changes between 22.1° and 24.5° — affecting how extreme our seasons are! 🎿❄️🏖️

19.1.3 🔄 Cycle 3: PRECESSION (~23,000 years)

THE SPIN: Earth’s axis wobbles like a spinning top 🌀 — changing which hemisphere points toward the Sun when we’re closest! This affects whether Northern or Southern summers are INTENSE.

19.2 🔬 INVESTIGATION LAB: Crack the Climate Code! 🕵️

⚡ TIME TO BECOME AN ORBITAL DETECTIVE! ⚡

19.2.1 🎒 Materials:

  • Graph paper or spreadsheet 📊
  • Colored pencils 🎨
  • Calculator 🧮
  • Your detective skills 🔍

19.2.2 📋 Mission Steps:

STEP 1: Analyze the Cycles 🌀

  1. Use the interactive simulations above to explore each cycle
  2. Record observations in your data table:
Cycle Period Current Value Range Climate Effect
Eccentricity ~100,000 yrs 0.017 0.0 - 0.06 Changes total radiation received
Obliquity ~41,000 yrs 23.5° 22.1° - 24.5° Changes seasonal contrast
Precession ~23,000 yrs N/A 360° rotation Changes timing of seasons

STEP 2: Connect to the Data 📈

Go back and review that radiation graph from the beginning!

  1. 🎯 Which cycle’s period matches the big 100,000-year pattern?
  2. 🌊 Could the other two cycles explain the smaller “wiggles”?

STEP 3: Make Your Claim 🎤

📣 YOUR VERDICT: Do Earth’s orbital cycles CAUSE those radiation changes? Back it up with EVIDENCE from the models and data!

20 Explain: Connecting Orbit to Climate

🧊 THE MILLION-DOLLAR QUESTION 🧊

Did Earth’s orbital wobbles ACTUALLY cause Ice Ages? 🤔

20.1 🌍 THE SECRET MECHANISM REVEALED

💥 PLOT TWIST: It’s not about total yearly radiation — it’s about SUMMER radiation at 65°N (high northern latitudes)!

20.1.1 Why 65°N Matters:

  1. Most of Earth’s land mass is in the Northern Hemisphere
  2. Ice sheets grow when summer is NOT warm enough to melt winter snow
  3. When summer radiation at 65°N is LOW, ice sheets expand
  4. When summer radiation at 65°N is HIGH, ice sheets retreat

20.1.2 The Feedback Loop:

Low summer radiation → Snow persists → Ice sheets grow → 
Higher albedo → More cooling → More ice growth

20.2 Comparing Radiation and Temperature

20.2.1 💡 Key Ideas: Earth-Sun Dynamics

  1. Temperatures on Earth have fluctuated greatly during human history, marked by glacial and interglacial periods
  2. A pattern exists in the frequency of these fluctuations (~100,000 years)
  3. The pattern is explained by cyclical changes in Earth’s orbit shape and tilt
  4. These changes cause ice sheets to expand and retreat
  5. Current orbital parameters suggest Earth should be cooling, yet global temperatures are increasing

21 Elaborate: Solar Activity vs. Glacial Cycles

☀️ BUT WAIT… WHAT ABOUT THE SUN? ☀️

21.1 🔥 Solar Activity Data

🤔 NEW THEORY ALERT: Some people say the Sun itself is getting brighter, causing climate change. We know orbital wobbles caused Ice Ages… but what about the Sun’s OUTPUT? Let’s investigate! 🕵️

21.1.1 ✅ Analysis Questions

  1. Has solar output increased significantly since 1980?
  2. Has temperature increased significantly since 1980?
  3. Can changes in solar output explain recent warming? Why or why not?

22 Evaluate: Are Orbital Factors Causing Warming Today?

🚨 THE FINAL VERDICT 🚨

So… are Earth’s orbital cycles causing climate change RIGHT NOW? 🌡️

22.1 📊 THE EVIDENCE SAYS…

Based on current orbital parameters:

Parameter Current Value Trend Climate Effect
Eccentricity 0.017 Decreasing Less seasonal variation
Obliquity 23.44° Decreasing Less extreme seasons
Precession NH summer at aphelion Changing slowly Cooler NH summers

Conclusion: Based on Milankovitch cycles alone, Earth should be gradually cooling. The fact that Earth is warming despite this indicates another factor is at play.

This sets up our next investigation: What IS causing the warming?


22.2 🎮 CHALLENGE MODE: Test Your Knowledge! 🏆

🔥 Can you ace this quiz? Let’s find out! 🔥